1. Field of the Invention
The present invention relates to a duct, and more particularly, to a duct that can be used for installation in vehicles.
2. Description of Prior Art
In general, ducts are installed at prescribed locations in vehicles, such as automobiles. For example, air conditioner ducts are installed behind the instrument panel and above the ceiling in an automobile. In a vehicle in which an air conditioner duct (in other words, a duct for a vehicle air conditioners) is installed as described above, the air blown out of the air conditioner mounted in the vehicle is directed through the space in the duct to outlets in the cabin.
Different vehicles have different shapes and structures, and the ducts are required to have a wide variety of shapes and structures according to the variations of vehicles. To meet the requests, hollow blow-molded articles made of a resin material have been favorably used for ducts. In this case, blow-molded articles employed are made of a non-foam resin.
As for ducts, there are problems of noise, such as a problem of leakage of the sound from the compressor of the vehicle air conditioner or the whistling sound of air flowing through the ducts into the cabin through the ducts and a problem of transmission of vehicle exterior noise or engine sound from the engine room into the cabin through the ducts. Thus, ducts having sound deadening properties have been desired. In this respect, a technique has been proposed to provide a duct having sound deadening properties by bonding a sound absorbing material to an outer surface of a duct (Japanese patent publication No. JP-A-H06-156051).
In addition, with recent increasing demand for weight reduction and compact structural design of vehicles, there is an increasing demand for ducts that are lighter in weight and have sound deadening properties. Thus, a technique has been proposed to use, for a duct, a foamed blow-molded article which is lighter in weight than that of a non-foam resin blow-molded article and excels in sound deadening properties (Japanese patent publication No. JP-A-2004-116959).